linux-kernel - Re: [PATCH] module param_call: fix potential NULL pointer dereference

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Message-ID: <2375c9f91002212337l543795d5ndb24173dd19e039e@mail.gmail.com>
Date:	Mon, 22 Feb 2010 15:37:00 +0800
From:	Américo Wang <xiyou.wangcong@...il.com>
To:	DDD <dongdong.deng@...driver.com>
Cc:	rusty@...tcorp.com.au, davem@...emloft.net,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	jason.wessel@...driver.com, lenb@...nel.org, dwmw2@...radead.org,
	mdharm-usb@...-eyed-alien.net, bfields@...ldses.org,
	robert.richter@....com
Subject: Re: [PATCH] module param_call: fix potential NULL pointer dereference

On Sun, Feb 21, 2010 at 5:16 PM, DDD <dongdong.deng@...driver.com> wrote:
> Américo Wang wrote:
>>
>> On Sun, Feb 21, 2010 at 3:24 PM, Dongdong Deng
>> <dongdong.deng@...driver.com> wrote:
>>>
>>> The param_set_fn() function will get a parameter which is a NULL
>>> pointer when insmod module with params via following method:
>>>
>>> $insmod module.ko module_params
>>>
>>> BTW: the normal method usually as following format:
>>> $insmod module.ko module_params=example
>>>
>>> If the param_set_fn() function didn't check that parameter and used
>>> it directly, it could caused an OOPS due to NULL pointer dereference.
>>>
>>> The solution is simple:
>>> Just checking the parameter before using in param_set_fn().
>>>
>>> Example:
>>> int set_module_params(const char *val, struct kernel_param *kp)
>>> {
>>>       /*Checking the val parameter before using */
>>>       if (!val)
>>>               return -EINVAL;
>>>       ...
>>> }
>>> module_param_call(module_params, set_module_params, NULL, NULL, 0644);
>>>
>>
>> Why not just checking all of them in the generic code?
>
> It is no problem that we check the params before invoking param_set_fn().
>
> But I trend to do the checking in param_set_*fn(), because we can offer some
> special prompt infos to user if we want and handle some special cases like
> param_set_bool().
>

Yeah, I knew standard bool parameters can accept that,
the problem is that KPARAM_ISBOOL is not enough to
check if a parameter is bool or not. Probably we need
a new flag...

Thanks.
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